Structural changes and shrinkage of potato during frying

Light microscopy was used to study changes in cell size, blister formation and crust evolution during potato frying. Frying experiments with both Fren ch fries and crisps of different thickness (1-5 mm) were performed at tempe ratures of 140 and 180 degreesC. Thickness, volume and density changes were also measured. The formation of crust in French fries starts after the pot ato surface reached approximately 103 degreesC, and then the crust thicknes s increased linearly with the square root of frying time, this increase bei ng faster at 180 degreesC. The potato volume decreased during frying, altho ugh in the late stages the volume may increase because of oil uptake and ce ll separation caused by entrapped water vapour. Shrinkage was adequately de scribed by the Weibull model with a residual value, with shrinkage rate inc reasing with temperature and decreasing with potato thickness. The residual volume was not affected by temperature (65% for French fries and 59-30 for crisps, depending on thickness). Volume appeared to decrease mainly as the result of water loss, except for very low water content, and thus potato d ensity changes were very small.